THE LYME-DISEASE VACCINE CANDIDATE OUTER SURFACE PROTEIN-A (OSPA) IN A FORMULATION COMPATIBLE WITH HUMAN USE PROTECTS MICE AGAINST NATURAL TICK TRANSMISSION OF BORRELIA-BURGDORFERI

Development of a vaccine for the Lyme disease spirochete, Borrelia bur gdorferi, has focused on the bacterial lipoprotein, major outer surfac e protein A (OspA). With few exceptions, testing of OspA vaccines in a nimal models has involved challenge with needle inoculation of culture d spirochetes. Recombinant OspA proteins from two OspA divergent strai ns of B. burgdorferi were tested for their vaccine potential in three different strains of mice challenged with laboratory, reared ticks wit h a high rate of B. burgdorferi infection. All formulations of the B. burgdorferi sensu stricto derived OspA vaccine protected all strains o f mice when challenged by ticks infected with an OspA homologous strai n of the spirochete, whereas heterologous OspA from B. afzelii did not protect. Furthermore, ticks feeding on protected mice had reduced Osp A levels compared to unvaccinated controls.